Effects of Hemoglobin C and S Traits on Glycohemoglobin Measurements by Eleven Methods

Patients with diabetes mellitus routinely have glycohemoglobin (GHb) testing performed to monitor glycemic control and assess risk for developing complications of their disease (1). The accuracy of several GHb methods can be adversely affected by the presence of hemoglobin (Hb) C or S trait (2)(3)(4)(5)(6). It has been estimated that there are at least 200 000 Americans with diabetes mellitus who also have either Hb C or S trait (6). We have recently shown that the presence of Hb C or S trait does not affect the accuracy of GHb measurements made by the CLC 330 boronate affinity HPLC method (7). We therefore evaluated the effects of Hb C and S traits on 11 commercial GHb methods, using the CLC 330 assay as the comparison method.Whole blood samples from individuals homozygous for Hb A (n = 73) and heterozygous for Hb C or S (n = 46 and 76, respectively) were collected in EDTA-containing tubes. After routine clinical testing had been completed, Hb variants were identified by inspection of chromatograms obtained with a VARIANT analyzer (Bio-Rad Laboratories) and the Beta Thal Short program run according to the manufacturer’s instructions. Aliquots of these samples that had 4–14% Hb A1c were stored at 2–8 °C and analyzed within 10 days of collection except for aliquots for the HA8160 and HA8160 Beta Thal (BT) methods, which were shipped on dry ice and stored frozen until analysis. Not all samples were analyzed by each analytic method. This study was approved by the Institutional Review …